JPH0224598B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Description of the Technical Field The present invention relates to a method for treating organic sludge such as sewage sludge and human waste sludge, and an object of the present invention is to provide a dewatering/drying method that has a particularly large energy-saving effect. .

(2) Description of conventional technology Organic sludge such as sewage sludge is conventionally dehydrated using a centrifugal dehydrator, belt press, filter press, screw press, etc. after adding dehydration aids such as cationic polymers, ferric chloride, and slaked lime. Although it is dehydrated in a machine and then dried, the current situation is that the drying process requires a large amount of auxiliary fuel such as heavy oil.
There is an urgent need to develop energy-saving dehydration and drying processes.

(3) Purpose of the present invention The purpose of the present invention is to provide a process that can rationally dehydrate and dry organic sludge without using any auxiliary fuel.

(4) Structure of the Invention The present invention involves adding and mixing paper to organic sludge, dewatering it using a screw press dehydrator, and then granulating and molding the dehydrated cake and filling it into a sealable container. A treatment for organic sludge, characterized in that this dehydrated cake is dried by direct contact with the discharge air of an aeration blower that supplies air to the biological treatment process of organic wastewater, and the outflow air is supplied to the biological treatment process. It's a method.

(5) Embodiments of the invention The present invention will be specifically explained based on embodiments shown in the drawings.

Taking sewage sludge as a typical example of organic sludge, waste paper 2 such as old newspapers is added to sewage sludge 1 (any of primary settled sludge, mixed raw sludge, or digested sludge), and the mixture is poured into a mixing tank 3. Mix thoroughly.

In addition, it is more suitable to previously disintegrate the waste paper 2 using a hydropulper to form a pulp slurry in order to improve the dehydration promoting effect.

Sludge 4 that has been thoroughly mixed with paper may be dehydrated as is using a screw press dehydrator.
When aiming to improve SS recovery rate and processing capacity, add polymer flocculant 5 (use of cationic polymer or a combination of cationic polymer and anionic polymer is effective) to flocculate, then screw press dehydration. The cake is dehydrated by a machine 6 and separated into a low-moisture dehydrated cake 7 and separated water 8.

In the present invention, it is essential to specify the screw press dehydrator as the dehydrating model; even if other dehydrating models are adopted, the effect of significantly reducing the water content of the dehydrated cake due to the addition of paper will not occur. I can't get it. Screw press dewatering machines use screws to compress and transport sludge under high pressure (over 10Kgf/ ^cm2 ), so pressure energy is converted into heat energy during the compression process, so the temperature of the dehydrated cake rises to over 50℃. do. As a result, the temperature of the dehydrated cake input into the next drying step is high, and the extremely important effect is that the amount of heat required for the drying operation is reduced. This effect cannot be obtained with other dehydrators.

Then, the dehydrated cake 7 is granulated and molded using a pelletizer 15 to form a granulated dehydrated cake ₇₁ , which is then stacked in a packed layer in a drying container 9 to form an aeration tank 10 in the activated sludge treatment process for sewage.
The discharged air 12 of the aeration blower 11 for supplying air is vented to the packed bed of the granulated dehydrated cake ₇₁ to bring it into direct contact with the packed bed, and is dried by the heat retained in the discharged air, and the dried product 13 is taken out. Drying container 9
Outflow air is supplied to the aeration tank 10 as aeration air 14.

The drying container 9 is a hermetically sealed container except that it has a supply port for the granulated dehydrated cake 7 ₁ , a dry material takeout port, and an inlet and _an outlet for the blower discharge air. directly,
They are brought into contact within the drying container 9.

As described above, in the present invention, the drying container 9 is a sealable container, the container is filled with the granulated dehydrated cake 7 ₁ obtained by granulating and molding the dehydrated cake 7, and the blower discharge air 12 is filled in this packed bed. By ventilating the granulated dehydrated cake ₇₁ , it is possible to prevent the granulated dehydrated cake 71 from sticking to each other and forming lumps in the drying container, and it also facilitates fluidized bed drying and makes it possible to use the retained heat of the discharged air 12. Thermal efficiency and heat transfer rate are extremely excellent, and the drying rate is significantly improved.

(6) Functions and Effects of the Invention The present invention provides that the discharge air of the aeration blower rises significantly above the intake air temperature by 60 to 70°C, as is clear from the adiabatic compression theory of gases in thermodynamics.
Focusing on this, we pre-granulated and molded a Screw Press dehydrated cake to which paper had been added, filled this granulated product into a drying container, and vented air discharged from an aeration blower through it. This method not only dries the granulated material by directly contacting it, but also guides the air (dried exhaust gas) flowing out from the dryer to the aeration tank for activated sludge treatment. It has high utilization efficiency and can dry sludge extremely efficiently without using auxiliary fuel such as heavy oil. As a result, significant energy savings can be achieved.

(b) Since paper is added to the sludge before dewatering, the dewatering process can be carried out efficiently as described below, and the moldability of the dehydrated cake is good, making granulation processing easy. can.

(c) There is a remarkable advantage that the odor of the dry exhaust gas is biologically deodorized by the microorganisms in the aeration tank, and dust removal treatment is also performed at the same time.

Moreover, since paper is added to organic sludge and dewatered using a screw press, squeezing pressure is applied to the sludge very effectively and a dehydrated cake with an extremely low water content of 45 to 50% can be obtained. As a result, the amount of water to be removed by drying is reduced, and the retained heat of the air discharged from the aeration blower makes it possible to easily obtain a dried material with a moisture content of 10 to 15% useful as a fuel.

Example: To the surplus sludge (SS concentration 3%) from the activated sludge treatment process generated from the human waste treatment plant in Zushi City, Kanagawa Prefecture, old newspapers previously disintegrated with a hydropulper were added to 100% of the solid content of the surplus activated sludge. After thorough mixing, DAM-based cationic polymer was added at 0.5% based on the solids of the excess activated sludge and coagulated. This flocculated sludge has a diameter of 150mmφ and a length of 2150mm.
screw press dehydrator (Ebara Infilco Co., Ltd.)
When dehydrated with the product, there was no stickiness at all.
A crisp paper-containing dehydrated cake with a significantly low moisture content of 48-50% was obtained. When this dehydrated cake was granulated to a particle size of 10 to 30 mm using an extrusion granulator, the dehydrated cake containing paper had good moldability and could be easily granulated.

This granulated material was supplied to a cylindrical container with a diameter of 1000 mmφ and a height of 2000 mm to form a packed bed of the granulated material. Since the heat utilization efficiency improves as the packed layer thickness increases, the layer thickness was set to 1 m. Since it is a granular material with a low moisture content and contains paper, it is not sticky and has sufficient strength, and there was no problem that the particles constituting the packed bed would adhere to each other due to compaction and become lumpy. As a result, uniform voids in the packed bed were sufficiently secured, and even when the air discharged from the aeration blower was ventilated, there was no uneven flow, and uniform aeration was achieved.

In order to obtain high drying thermal efficiency by using low-temperature energy such as the air discharged from an aeration blower, which has a maximum temperature of about 70°C, it is necessary to adjust the physical properties of the dehydrated cake that is input into the drying process to improve adhesion, as in this method. It has been recognized that the most important point is to reduce the amount of carbon dioxide and to increase the strength of the cake so that compaction and adhesion do not occur even when a thick packed layer is formed.

When aeration blower discharge air at a temperature of 70°C was passed through a packed bed at a superficial velocity of 0.1 m/s for 1 hour and 30 minutes, paper-containing granular dehydrated cake with a moisture content of 48 to 50% was found to have a moisture content of 8 to 10%. It becomes a dry product and has a lower calorific value.
A solid fuel with a high calorie content of 3800 to 3900 kcal/Kg dry matter, good ignitability, and granular shape with good handling properties was obtained.

On the other hand, for comparison, when the cationic polymer was added to surplus activated sludge without paper and dewatered using a screw press, the dehydration performance was poor and the water content was low.
It was not possible to lower it below 76%.

As a result, the dehydrated cake was sticky and had poor granulation properties, so it was fed to the drying container without granulation, but if the layer thickness was 30 cm or more, the lower part would be consolidated, so if the layer thickness was 20 cm or more, the lower part would be consolidated. I did a test. However, after passing the air for 1.5 hours at a superficial velocity of 0.1 m/s, the moisture content of the dry matter was 10.
It had large spots of ~30% and lacked properties as a solid fuel.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of an embodiment of the present invention. 1... Sewage sludge, 2... Waste paper, 3... Mixing tank,
4... Sludge, 5... Polymer flocculant, 6... Screw press dehydrator, 7... Dehydrated cake, 7 ₁ ...
Granulated dehydrated cake, 8...separated water, 9...drying container, 10...aeration tank, 11...aeration blower, 12...discharge air, 13...dried material, 14...aeration air, 15...Pelletizer.

Claims (1)

[Claims] 1. After adding and mixing paper to organic sludge, dewatering it with a screw press dehydrator, and then granulating and molding the dehydrated cake and filling it into a sealable container,
A treatment for organic sludge, characterized in that this dehydrated cake is dried by direct contact with the discharge air of an aeration blower that supplies air to the biological treatment process of organic wastewater, and the outflow air is supplied to the biological treatment process. Method.